If your treatments are likely to have influenced the quality of harvested products or the capacity of your paddock to profitably support future crops then it’s probably a good idea to consider a range of after-harvest measurements as part of the current trial.

In some trials, the after-harvest effects of treatments will have an important bearing on their relative profitability. These might include:

• Treatments that influence the amount or type of crop residues. These will impose costs of incorporation or disposal that need to be taken into account if your trial objective was to investigate effects on gross margin. Residues may help to preserve soil structure but may also help to harbour pests and diseases. If these are likely to impact on the gross margin from the different treatments then they should be taken into account as part of your trial.
• Treatments that influence soil conditions. The extent to which these carry over to other seasons or crops will impact on the relative productivity and profitability of the treatments that you have just considered as part of your trial. You may want to know whether the treatments have influenced soil fertility, structure, moisture or some other factor. If so, there is no substitute for measurement of either direct or proxy variables.
• Treatments that influence the timing of key events, such as sowing and harvest. These sorts of changes can have a big impact on the timing of subsequent management events (such as tillage) and on the types of crops and productivity that can occur after the trial crop is finished with. The economic and practical value of these phenomena is likely to influence the real value of the treatments just tested.

End of section critical decision point

Would measurements of additional variables such as product quality, soil properties or productivity of subsequent crops provide a more complete picture of the value and implications of the treatments that you’ve just tested? If so, you may want to give thought to additional after-trial measurements or even a post-trial trial. If this isn’t required, now’s the time to get into the numbers in the next section – “Analysing the trial results”.